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Shape-shifting liquid metals for electronics that build themselves

Static circuit boards may one day give way to dynamic, changeable ones that can pop up on demand.

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Shape-shifting electronic circuits that can self-assemble are inching closer. Engineers in Australia and Switzerland have manipulated the movements and shape of a drop of liquid metal by adjusting the acidity of its watery environment.

The team, led by Melbourne’s RMIT University’s Kourosh Kalatar-zadeh, says the work could help dynamic elastic electronic components that move autonomously to create new circuits, rather than be stuck in the one arrangement.

While the liquid metal T-1000 from the Terminator franchise is still well and truly in the realm of science fiction, Kalatar-zedah and his colleagues wondered if they could borrow its fluidity and shape-shifting qualities to create electronic circuits.

Alloys of gallium are ideal candidates: the liquid metal is malleable and conductive. Could the researchers manipulate gallium alloys easily without touching them?

First, they popped droplets of the alloy galinstan (a portmanteau of gallium, indium and stannum) in water and adjusted the water's pH and salt concentration to see how the galinstan droplet reacted.

They found the edges of the droplet deformed inwards in an acidic bath and bulged outward in a base. Adding sodium chloride, or plain old table salt, to the mix increased the bulging.

Using hydrogen chloride as the acid, sodium hydroxide as the base and salt, they produced switches and pumps by propelling galistan droplets around in fluid-filled tubes.